/************************************************************************************[SimpSolver.h]
Copyright (c) 2006,      Niklas Een, Niklas Sorensson
Copyright (c) 2007-2010, Niklas Sorensson

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute,
sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
**************************************************************************************************/

#ifndef Minisat_SimpSolver_h
#define Minisat_SimpSolver_h

#include "minisat/core/Solver.h"
#include "minisat/mtl/Queue.h"

namespace Minisat {

//=================================================================================================

class SimpSolver : public Solver
{
  public:
	// Constructor/Destructor:
	//
	SimpSolver();
	~SimpSolver();

	// Problem specification:
	//
	Var newVar(lbool upol = l_Undef, bool dvar = true);
	void releaseVar(Lit l);
	bool addClause(const vec<Lit>& ps);
	bool addEmptyClause();						// Add the empty clause to the solver.
	bool addClause(Lit p);						// Add a unit clause to the solver.
	bool addClause(Lit p, Lit q);				// Add a binary clause to the solver.
	bool addClause(Lit p, Lit q, Lit r);		// Add a ternary clause to the solver.
	bool addClause(Lit p, Lit q, Lit r, Lit s); // Add a quaternary clause to the solver.
	bool addClause_(vec<Lit>& ps);
	bool substitute(Var v, Lit x); // Replace all occurences of v with x (may cause a contradiction).

	// Variable mode:
	//
	void setFrozen(Var v, bool b); // If a variable is frozen it will not be eliminated.
	bool isEliminated(Var v) const;

	// Alternative freeze interface (may replace 'setFrozen()'):
	void freezeVar(Var v); // Freeze one variable so it will not be eliminated.
	void thaw();		   // Thaw all frozen variables.

	// Solving:
	//
	bool solve(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	lbool solveLimited(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	bool solve(bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, Lit q, bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, Lit q, Lit r, bool do_simp = true, bool turn_off_simp = false);
	bool eliminate(bool turn_off_elim = false); // Perform variable elimination based simplification.

	// Memory managment:
	//
	virtual void garbageCollect();

	// Generate a (possibly simplified) DIMACS file:
	//
#if 0
    void    toDimacs  (const char* file, const vec<Lit>& assumps);
    void    toDimacs  (const char* file);
    void    toDimacs  (const char* file, Lit p);
    void    toDimacs  (const char* file, Lit p, Lit q);
    void    toDimacs  (const char* file, Lit p, Lit q, Lit r);
#endif

	// Mode of operation:
	//
	int grow;			 // Allow a variable elimination step to grow by a number of clauses (default to zero).
	int clause_lim;		 // Variables are not eliminated if it produces a resolvent with a length above this limit.
						 // -1 means no limit.
	int subsumption_lim; // Do not check if subsumption against a clause larger than this. -1 means no limit.
	double
		simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').

	bool use_asymm;	   // Shrink clauses by asymmetric branching.
	bool use_rcheck;   // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
	bool use_elim;	   // Perform variable elimination.
	bool extend_model; // Flag to indicate whether the user needs to look at the full model.

	// Statistics:
	//
	int merges;
	int asymm_lits;
	int eliminated_vars;

  protected:
	// Helper structures:
	//
	struct ElimLt
	{
		const LMap<int>& n_occ;
		explicit ElimLt(const LMap<int>& no)
			: n_occ(no)
		{
		}

		// TODO: are 64-bit operations here noticably bad on 32-bit platforms? Could use a saturating
		// 32-bit implementation instead then, but this will have to do for now.
		uint64_t cost(Var x) const { return (uint64_t)n_occ[mkLit(x)] * (uint64_t)n_occ[~mkLit(x)]; }
		bool operator()(Var x, Var y) const { return cost(x) < cost(y); }

		// TODO: investigate this order alternative more.
		// bool operator()(Var x, Var y) const {
		//     int c_x = cost(x);
		//     int c_y = cost(y);
		//     return c_x < c_y || c_x == c_y && x < y; }
	};

	struct ClauseDeleted
	{
		const ClauseAllocator& ca;
		explicit ClauseDeleted(const ClauseAllocator& _ca)
			: ca(_ca)
		{
		}
		bool operator()(const CRef& cr) const { return ca[cr].mark() == 1; }
	};

	// Solver state:
	//
	int elimorder;
	bool use_simplification;
	Var max_simp_var; // Max variable at the point simplification was turned off.
	vec<uint32_t> elimclauses;
	VMap<char> touched;
	OccLists<Var, vec<CRef>, ClauseDeleted> occurs;
	LMap<int> n_occ;
	Heap<Var, ElimLt> elim_heap;
	Queue<CRef> subsumption_queue;
	VMap<char> frozen;
	vec<Var> frozen_vars;
	VMap<char> eliminated;
	int bwdsub_assigns;
	int n_touched;

	// Temporaries:
	//
	CRef bwdsub_tmpunit;

	// Main internal methods:
	//
	lbool solve_(bool do_simp = true, bool turn_off_simp = false);
	bool asymm(Var v, CRef cr);
	bool asymmVar(Var v);
	void updateElimHeap(Var v);
	void gatherTouchedClauses();
	bool merge(const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
	bool merge(const Clause& _ps, const Clause& _qs, Var v, int& size);
	bool backwardSubsumptionCheck(bool verbose = false);
	bool eliminateVar(Var v);
	void extendModel();

	void removeClause(CRef cr);
	bool strengthenClause(CRef cr, Lit l);
	bool implied(const vec<Lit>& c);
	void relocAll(ClauseAllocator& to);
};

//=================================================================================================
// Implementation of inline methods:

inline bool
SimpSolver::isEliminated(Var v) const
{
	return eliminated[v];
}
inline void
SimpSolver::updateElimHeap(Var v)
{
	assert(use_simplification);
	// if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
	if (elim_heap.inHeap(v) || (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
		elim_heap.update(v);
}

inline bool
SimpSolver::addClause(const vec<Lit>& ps)
{
	ps.copyTo(add_tmp);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addEmptyClause()
{
	add_tmp.clear();
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p)
{
	add_tmp.clear();
	add_tmp.push(p);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p, Lit q)
{
	add_tmp.clear();
	add_tmp.push(p);
	add_tmp.push(q);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p, Lit q, Lit r)
{
	add_tmp.clear();
	add_tmp.push(p);
	add_tmp.push(q);
	add_tmp.push(r);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p, Lit q, Lit r, Lit s)
{
	add_tmp.clear();
	add_tmp.push(p);
	add_tmp.push(q);
	add_tmp.push(r);
	add_tmp.push(s);
	return addClause_(add_tmp);
}
inline void
SimpSolver::setFrozen(Var v, bool b)
{
	frozen[v] = (char)b;
	if (use_simplification && !b) {
		updateElimHeap(v);
	}
}

inline void
SimpSolver::freezeVar(Var v)
{
	if (!frozen[v]) {
		frozen[v] = 1;
		frozen_vars.push(v);
	}
}

inline void
SimpSolver::thaw()
{
	for (int i = 0; i < frozen_vars.size(); i++) {
		Var v = frozen_vars[i];
		frozen[v] = 0;
		if (use_simplification)
			updateElimHeap(v);
	}
	frozen_vars.clear();
}

inline bool
SimpSolver::solve(bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, Lit q, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	assumptions.push(q);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, Lit q, Lit r, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	assumptions.push(q);
	assumptions.push(r);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(const vec<Lit>& assumps, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumps.copyTo(assumptions);
	return solve_(do_simp, turn_off_simp) == l_True;
}

inline lbool
SimpSolver::solveLimited(const vec<Lit>& assumps, bool do_simp, bool turn_off_simp)
{
	assumps.copyTo(assumptions);
	return solve_(do_simp, turn_off_simp);
}

//=================================================================================================
}

#endif
